Apparatus for surveillance of arc discharge lamps



Dec. 20, 1966 L. w. KIMBALL 3,292,988

APPARATUS FOR SURVEILLANCE OF ARC DISCHARGE LAMPS Filed April '7, 1964 2 Sheets-Sheet 1 v v 1) 10 i I! W f fiDdL j V EF Lfl /0 zzmr/vz //V57k(/MENT RESPONSE n/vasr/eoM um/zs j 0 i J" z INVENTOR. jaw mare KZ'iWid/l Dec. 20, 1966 L. w. KIMBALL APPARATUS FOR SURVEILLANCE OF ARC DISCHARGE LAMPS Filed April 7, 1964 2 Sheets-Sheet .2

United States Patent 3,292,988 APPARATUS FOR SURVEILLANCE 0F ARC DISCHARGE LAlVIPS Lawrence W. Kimball, Bedford, Mass., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Apr. 7, 1964, Ser. No. 357,882 Claims. (Cl. 316-32) This invention relates to apparatus used in association with are discharge lamps during their manufacture or use, and particularly to surveillance apparatus for inspecting or controlling mercury filled fluorescent lamps.

For example, in production line manufacture of fluorescent lamps, a glass tube is coated internally with a phosphor, electron emissive electrodes are mounted at each end of the tube, the tube is exhausted, and a fill of mercury and a small amount of rare gas such as argon is sealed in the tube at low pressure. Then terminal bases are attached to the tube and other finishing operations are performed. To attain proper lamp quality control it is desirable to determine as early as possible that the lamp contains mercury vapor and an additional quantity of liquid mercury to maintain, at operating temperatures, a mercury vapor pressure suflicient to produce an arc discharge in the ultraviolet spectrum for exciting secondary emission of the phosphor coating of the lamp as well as mercury resonance emission in the visible spectrum.

Thus, one object of the invention is to provide a way of inspecting lamps upon their completion, or preferably prior to the aforementioned finishing operations, so that inadequate mercury filling can be detected before a large number of defective lamps are completed.

It is also desirable to maintain optimum light output of a correctly filled lamp during use by control of its mercury vapor pressure. One lamp whose mercury vapor pressure is conveniently controlled over a wide range of ambient temperatures is a lamp of the high thermal, very high output (VHO) type having on its inner surface a small area of mercury-amalgamative metal such as indium. Mercury pressure is decreased by amalgamation of mercury with the metal, and increased by external heating of the metal area to vaporize mercury amalgamated with it.

A further object of this invention is to provide an improved way of sensing vapor pressure variations in controllable lamps, such as that described above, so that the proper control can be applied. Thus the invention involves surveillance of a lamp for the purposes of control as well as inspection.

I have found a very sensitive way of measuring the vapor pressure of arc discharge lamps with a fill of vaporizable, positively ionizable material such as mercury resonant in the ultra-violet and visible spectra and a rare gas resonant in the red to infrared spectra, the amplitude of rare gas emission being suppressed over a correlated range of mercury emission at different vapor pressures. Such sensitive measuring is attained by exciting to fill the light emission, filtering the light to exclude substantial radiation below approximately 6500 angstrom units, measuring the value of the light so filtered, and comparing said measured value with the correlated range of mercury emission thereby to indicate the vapor pressure of the mercury. Such a sensing affords far more successful surveillance than measurement of mercury excited or primary mercury emission alone, since an insuflicient amount of mercury, for example, can produce fairly strong total emission.

Further the invention relates to apparatus for surveillance of an arc discharge lamp normally emitting light energy predominantly at predetermined frequencies, said apparatus comprising means to support the lamp, means to Patented Dec. 20, 1966- apply excitation energy to the lamp, a photoelectric device adjacent the lamp selectively responsive to a change from normal emission to emission at different frequencies, and means actuated by said device for acting on the lamp in accordance with its emission condition.

For the purpose of illustration, typical embodiments of the invention are shown in the accompanying drawings in which:

FIG. 1 is a graph showing relative normal and abnormal emission of a fluorescent lamp;

FIG. 2 is a schematic diagram of apparatus for controlling the light output of a fluorescent lamp;

FIG. 3 is a graph showing the light output of a high thermal VHO lamp at various ambient temperatures;

FIG. 4 is an isometric view, partly broken away, of a high thermal VHO lamp and its heater; and

FIG. 5 is a schematic diagram of apparatus for inspecting fluorescent lamps during manufacture.

Shown in FIG. 1 is the distribution of the spectral energy of Warm white high thermal VHO lamps. Curve L1 represents the emission of such a lamp with an adequate mercury fill; curve L2 represents a like lamp with substantially no mercury. With mercury the lamp energy is distributed between roughly 4000 and 7000 angstrom units. Only the upper end of the curve is shown here to illustrate relative distribution of red and near infrared energy on curve L2. This energy appears in strong narrow argon resonance bands at 6965, 7067, 7272, 7383, 7503, 7635, 7723, 7945 and 8115 angstroms. I have found not only that this emission predominates when suflicient mercury is lacking in a lamp, but also that in a lamp with sufficient mercury the red emission beyond 6500 A. is suppressed as the mercury emission increases depending upon the amount of mercury available and hence the mercury vapor pressure. While the above example is typical, other fill gases such as neon, krypton and xenon have resonance bands close to or beyond 6500 A. which predominate or are suppressed as mercury is inadequate or suflicient. For a given lamp type there is a correlation between the amplitude of rare gas emission and mercury emission, temperature or' pressure over a range of mercury emission. By varying the temperature of a lamp, and hence its vapor pressure over the common operating range of values, and measuring the correlated amplitude values of red to infrared emission a plot of red to infrared emission versus vapor pressure can be made. Then the operating condition of a questionable lamp may be determined by exciting the lamp, filtering out its light emission below about 6500 A., measuring the filtered light and comparing the measurement with the correlated plot. A meter M for the purpose is shown in FIG. 5 in connection with a suitable light filter and photocell.

According to the form of invention shown in FIG. 5 the variation in spectral distribution of lamp energy is used to detect defective lamps early in their manufacture. FIG. 5 shows schematically a production line comprising a conveyor 1 for moving the glass lamp envelope L through various stations. Envelopes which have in previous stations been prepared and coated internally with a phosphor are conveyed past a station 2 at which a mercury fill is added, a station 3 where the atmosphere is exhausted from the envelope and the fill gas added, a station 4 where the mercury and gas fill is sealed within the envelope, then to an inspection station 6 and a rejection station 7 at which defective lamps are ejected from the conveyor.

At the inspection station 6 there is a generator of radio frequency energy 61 connected to a field coil 62 which applies an intense RF electromagnetic field to the lamp L passing through the station 6. With a 27 megacycles, 60 watt generator, the field is suflicient to excite the mercury, if any, and argon in the lamp to their characteristic emission.

The emission from the lamp L at the inspection station is under the surveillance of a photoelectric relay circuit 9 comprising a photocell 91, a thyratron 96 and a relay 97. The photocell 91 is, for example, a poly crystalline cadmium selenide cell (Clairex type GL3, CL403 or CL603) exposed through a red filter such as Kodak- Wratten gelatine filter No. 89B. A typical response curve for a photocell so filtered is shown at P1 in FIG. 1. The photocell is connected across the 125 volt A.C. secondary of a 115 volt A.C. transformer T1 in series with a 0.05 microfarad blocking condenser, a to 50 thousand ohm potentiometer 94 and a 5 megohm potentiometer 95. The photocell 91 is also connected through a 100 thousand ohm resistor to the control grid of the thyratron. The relay 97 and thyratron 96 are connected in series across the A.C. supply, with a type 1N1764 diode in parallel with the relay for reducing relay chatter. The contactor 97a of the relay 97 is connected to an electrical ejecting mechanism 7.

In addition to 125 volt A.C. plate voltage for the thyratron 96, a six volt secondary of the transformer T1 supplies heating current to the thyratron filament. A common ground for the 125 volt and 6 volt secondaries is connected to the filament and cathode of the thyratron insuring that alternations in cathode voltage are in phase with alternations in grid voltage.

Coarse and fine adjustments of the voltage at the thyratron grid are provided by potentiometers 94 and 95 respectively. These are adjusted so that the thyratron is somewhat below cut-off when the photocell is illuminated by the normal emission of a lamp L in the spectral range below approximately 6500 A. Because of the filter 93 the resistance of the cell 91 is little aifected by normal illumination. When a lamp L with insufficient mercury is conveyed to the inspection station and emits in the red and infrared frequencies the resistance of the photocell is lowered and the voltage at the thyratron grid changes causing the thyratron to fire and energize the relay 97. The relay in turn energizes the ejecting mechanism 7 through contactor 97a causing the defective lamp to be removed from the production line. An additional relay contactor 97b energizes an auxiliary device such as a counter or an alarm which alerts the production line supervisor to the possibility of a malfunction of the mercury fill station 2.

FIG. 2 shows another form of surveillance apparatus for controlling the vapor pressure of a high thermal VHO fluorescent lamp 11. Such a lamp has known electrode structures connected to 2-pin terminal bases 12 at each end of the lamp. The high thermal lamp is characterized by an internal area of a mercury amalgamative metal. such as indium. In FIG. 4 the area is in the shape of a ring 13 at the middle of the lamp 11. Such a ring amalgamates with the mercury fill so. as to control mercury vapor pressure, and hence light output. Even at 140 F. ambient temperature, for example, well above the efficient range of conventional lamps, as shown by curve A of FIG. 3 the indium ring can prevent excess mercury vapor pressure. Fall off of light output as the ambient temperature drops below 140 F. can be avoided by providing the lamp with a heating collar 14 which includes a resistance heating wire 16 connected to terminals 17. The collar embraces the indium ring area 13 of the lamp 11, and its effect when supplied current is to heat the indium amalgamated mercury releasing it so as to increase the mercury pressure and provide a second optimum ambient temperature of about 40 F. on the second operating curve B of FIG. 3. By proper control of the heater, optimum pressure and light output can be maintained between 40 and 140 ambient temperature.

A particularly sensitive circuit for heater control of a high thermal VI-IO lamp is shown in FIG. 2. Therein the lamp 11 is shown schematically as supported in a fixture 10 by the socket connections 18 of the fixture. The 1 connectors are connected to a ballast 19 as is conventional.

The heating collar terminals 17 are connected to a control circuit within the fixture.

The control circuit includes a photocell 21 exposed through a red filter 22 to the light output of the lamp. The photocell may be a cadmium selenide cell such as 1 Clairex type CL603 with a Kodak-Wratten gelatine filter No. 87C.

by a 4.7 megohm resistor 26 when the contact 27 of a relay 28 is in the position shown in FIG. 2. The photocell and resistors 24 and 26 form a voltage divider which determines thevoltage at the grid of a type 2D21 thyratron 29. As will be explained in more detail the relay 28 through its contact 27 supplies heating current to the heating collar 14. The resistors 24 and 26 are selected i so that the ambient heat and the heat supplied by the collar heat the lamp just below the optimum temperature of curve A, e.g., 140 F. such that an increase in ambient temperature does not cause a decrease of the light output of the lamp 11. The relay 28 and thyraton 29 are connected in series across the volt supply A.C., the

relay coil being paralleled by a diode 31 such as type If by reason of a drop in ambient temperature the mercury content of the lamp diminishes by amalgamation with the indium ring 13 to the point where there. is insufiicient mercury vapor 1 1N1764 for minimizing relay chatter.

to maintain the light output just below optimum, the argon emission on the curve L2 simultaneously increases and 1 the resistance of the photocell 21 will therefore decrease,

raising the voltage at the thyratron grid above cutoff. The thyratron then fires drawing current through the relay 28 and transferring the relay contact 27. Transfer of the contact 27 connects the heater 14 across the secondary transformer terminals 23 thereby heating the indium ring and vaporizing some of the mercury amalgamated with the ring. Transfer of the relay contact 27 also disconnects the 4.7 kilohm resistance 26 from the voltage dividing circuit, thereby abruptly raising the voltage on the thyratron grid to a higher voltage above cutoif. This operation of the switch provides a dead zone of photocell control such that, to restore the thyratron grid voltage to cutoff, the photocell resistance must increase to a value higher than that at which, with the 4.7 kilohm resistance 26 in circuit, it raised the thyratron grid above cutoff.

When, by heating the indium ring 13, the mercury pressure is restored to optimum, the argon emission in the infrared is suppressed and increased photocell resistance drops the thyratron grid voltage below cutolf thereby deenergizing the relay 28, transferring contact 27 to the position shown and removing current from the heating collar 14.

In the foregoing description specific ways of controlling or measuring mercury vapor pressure have been disclosed. It should be understood, however, that the invention is not limited to these illustrative examples but is defined in the appended claims.

I claim:

1. Apparatus for surveillance of an arc discharge lamp normally emitting light energy predominantly at predetermined frequencies, said apparatus comprising means to support the lamp, means to apply excitation energy to' The photocell 21 is connected across the 12.6 1 volt secondary terminals 23 of a transformer T2 supplied from a 115 volt A.C. supply, the photocell also being in 1 series with a 620 kilohm resistor 24, which is paralleled l to support the lamp, means to apply excitation energy to the lamp, a photoelectric device adjacent the lamp selectively responsive to said abnormal frequencies of emission and means actuated by said device for acting on the lamp in accordance with its abnormal emission.

3. Apparatus for surveillance of an arc discharge lamp normally emitting light energy predominantly at frequencies below infrared and abnormally emitting light energy in the red to infrared, said apparatus comprising means to support the lamp, means to apply excitation energy to the lamp, a photoelectric device adjacent the lamp selectively responsive to red to infrared energy, and means actuated by said device for acting on the lamp in accordance with its red to infrared emission.

4. Apparatus for control of a mercury arc discharge lamp emitting light energy of predetermined frequencies at optimum vapor pressure operating temperature, said apparatus comprising means to support the lamp, means to supply excitation energy to the lamp, a photoelectric device adjacent the lamp selectively responsive to a change from normal emission, and means actuated by said device for controlling the temperature of the lamp to maintain emission at said predetermined frequencies.

5. Apparatus for control of a mercury arc discharge lamp having a fill of mercury emitting in the ultraviolent and visible spectra and a rare gas emitting in the red to infrared spectra, said apparatus comprising means to support the lamp, means to apply excitation energy to the lamp, a photoelectric device exposed to emission from the lamp, and means actuated by said device to control the temperature of the lamp, said photoelectric device comprising a photocell selectively responsive to light in the red to infrared spectra.

6. Apparatus for control of a mercury arc discharge lamp emitting light energy of predetermined frequencies at optimum vapor pressure operating temperature, said apparatus comprising means to support the lamp, means to supply excitation energy to the lamp, a photoelectric device adjacent the lamp selectively responsive to a change from normal emission, and means actuated by said device for heating the lamp so as to increase the vapor pressure in said lamp to maintain emission at said predetermined frequencies.

7. Apparatus for inspection of an arc discharge lamp during manufacture, said lamp normally emitting light energy of predetermined frequencies at operating vapor pressure, said manufacture including moving the lamp on a path through positions for filling said lamp with a vaporizable, positively ionizable material, sealing said material in the lamp, applying excitation energy to said filled and sealed lamp, said inspection apparatus comprising a photoelectric device at the position of said excitation applying means, said device being selectively responsive to light frequencies other than said predetermined frequencies, and means actuated by said device for rejecting a lamp from said path.

8. Apparatus for inspection of a mercury are discharge lamp during manufacture, said manufacture including moving the lamp on a path through a position for filling the lamp with mercury emissive in the ultraviolet and visible spectra and a rare gas emissive in the red to infrared spectra, and through a position for sealing the mercury and gas in the lamp and a position for applying excitation energy to the lamp, said inspection apparatus comprising a photoelectric device at the position for applying excitation energy, said photoelectric device being exposed to emission from said lamp and including a photocell selectively responsive to red to infrared light and relay means energized by said photocell when said red to infrared emission exceeds a predetermined value, and means actuated by said relay means for ejecting a lamp from said path.

9. Apparatus for the manufacture of an arc discharge lamp having a fill of mercury emissive in the'ultraviolet and visible spectra and a rare gas emissive in the red to infrared spectra comprising means for supplying said fill to the lamp, means for sealing said fill in the lamp, means for applying excitation energy to said filled and sealed lamp, conveyor means for moving said lamp to positions at said filling, sealing and excitation means, photoelectric relay means at the position of said excitation means, said relay means comprising a photocell primarily sensitive to red to infrared light above about 6500 Angstrom units, and means controlled by said relay means for indicating the emission of a lamp in the red to infrared spectra.

10. For determining the operating mercury vapor pressure in an arc discharge lamp having a fill of mercury resonant in the ultraviolet and Visible emission spectra and a rare gas resonant in the red to infrared emission spectra, the amplitude of rare gas emission being suppressed over a correlated range of mercury emission at different vapor pressures, the method which comprises exciting the fill to light emission, filtering the light to exclude substantial radiation below approximately 6500 Angstrom units, measuring the value of the light so filtered, and comparing said measured value with the correlated range of mercury emission thereby to indicate the vapor pressure of the mercury.

References Cited by the Examiner UNITED STATES PATENTS 2,456,396 12/1948 Frohock 3l632 RICHARD H. EANES, JR., Primary Examiner. 

1. APPPARATUS FOR SURVEILLANCE OF AN ARC DISCHARGE LAMP NORMALLY EMITTING LIGHT ENERGY PREDOMINANTLY AT PREDETERMINED FREQUENCIES, SAID APPARATUS COMPRISING MEANS TO SUPPORT THE LAMP, MEANS TO APPLY EXCITATION ENERGY TO THE LAMP, A PHOTOELECTRIC DEVICE ADJACENT THE LAMP SELECTIVELY RESPONSIVE TO EMISSION AT FREQUENCIES DIFFEREING FROM SAID PREDETERMINED FREQUENCIES AND MEANS ACTUATED BY SAID DEVICE FOR ACTING ON THE LAMP IN ACCORDANCE WITH ITS EMISSION CONDITION. 